WailingWalrus: Oh man, it's been awhile since I've heard the Thinksound IEM, and I've never heard the Vmoda M100. I have heard the RHA T20, though.
So, the HEM lineup has quite a range of sound signatures. I'd suggest you take a look at my HEM8 review. It contains a brief comparison there of each of the HEM IEM. Off the top of my head, I bet you'd immediately prefer HEM2. I know I clicked with it immediately coming from IEM like RHA T20 and FLC8S. In addition to my thoughts on HEM2 in my HEM8 review, I'd also point you to
shigzeo's excellent review of HEM2. It's the most enjoyable single BA IEM I've heard. They're also really damn comfortable. And
shigzeo snapped the cable with his bare hands like Superman, lol! (I haven't had any problems with it, though.)
With RHA T20, you'll get more bass impact without compromising bass clarity / resolution and crisper highs that some find fatiguing but can be controlled with the filters and tip selection. I'd suggest starting with the Bass filter abs foam tips until you've burned them in a bit age then moving up to the Reference for and then on to silicon tips. I'd also suggest avoiding the Treble filter unless you really, really like your highs to be ultra-defined. Due to the driver bass and treble presence, T20 also have a bit less mid presence. Comfort is good, but the memory wire section is a bit thick and is less ergonomic than the HEM cables. But in the other hand, there's no way
shigzeo is going to tear apart T20's cable, Superman strength notwithstanding
I hope that was useful. If you'd like to see some quick n dirty FR curves comparing the two, PM me